package com.shujia.java.day7;

public class Test1 {
    public static void main(String[] args) {
        StringBuffer  sb = new StringBuffer("123456789");
        int l =sb.length();
        for(int z =3 ;z<=l;z+=4){
            sb.insert(z,",");
            l =sb.length();
            if (z+4>=sb.length()){
                sb.insert(sb.length(),"。");
                break;
            }
        }
        System.out.println(sb);
    }
}

